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Database design --- Relational data bases. --- Data base design.

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In a relational database the information is recorded as rows in tables. However, in many practical situations the available information is incomplete and the values for some columns are missing. Yet few existing database management systems allow the user to enter null values in the database. This monograph analyses the problems raised by allowing null values in relational databases. The analysis covers semantical, syntactical, and computational aspects. Algorithms for query evaluation, dependency enforcement and updates in the presence of null values are also given. The analysis of the computational complexity of the algorithms suggests that from a practical point of view the database should be stored as Horn tables, which are generalizations of ordinary relations, allowing null values and Horn clause-like restrictions on these null values. Horn tables efficiently support a large class of queries, dependencies and updates.

Bases de données relationnelles --- Relational databases --- Relationele databases --- 681.3*H2 --- 681.3*I2 --- Relational data bases --- Databases --- Database management: security; integrity; protection--See also {?681.5*E5} --- Artificial intelligence. AI --- Relational databases. --- 681.3*I2 Artificial intelligence. AI --- 681.3*H2 Database management: security; integrity; protection--See also {?681.5*E5} --- Relational data bases. --- Data structures (Computer science). --- Database management. --- Algorithms. --- Artificial intelligence. --- Data Structures and Information Theory. --- Database Management. --- Algorithm Analysis and Problem Complexity. --- Artificial Intelligence. --- Data base management --- Data services (Database management) --- Database management services --- DBMS (Computer science) --- Generalized data management systems --- Services, Database management --- Systems, Database management --- Systems, Generalized database management --- Electronic data processing --- Information structures (Computer science) --- Structures, Data (Computer science) --- Structures, Information (Computer science) --- File organization (Computer science) --- Abstract data types (Computer science) --- AI (Artificial intelligence) --- Artificial thinking --- Electronic brains --- Intellectronics --- Intelligence, Artificial --- Intelligent machines --- Machine intelligence --- Thinking, Artificial --- Bionics --- Cognitive science --- Digital computer simulation --- Logic machines --- Machine theory --- Self-organizing systems --- Simulation methods --- Fifth generation computers --- Neural computers --- Algorism --- Algebra --- Arithmetic --- Foundations